I hope after she reaches the desired weight and you don't need to do the tube feeding anymore that she'll start eating enough on her own! Does she live with any other ducks? I find other ducks are handy for getting a duck to enjoy a certain food or treats that I'm wanting them to eat. Seeing the...
Sorry she's sick and so soon after losing your dog too! :(
IME, ducks with infections can seem fine other than not eating enough. I've seen this with ducks with respiratory infections, throat infections, etc. It's difficult to detect that anything is wrong until you notice the eating...